Device for shaping infarcted heart tissue and method of using the device

ABSTRACT

A device and method for treating an infarct scar on a heart comprising an electric cable with proximal and distal ends; a handle with proximal and distal ends with the proximal end connected to the distal end of the cable; a stem with proximal and distal ends with the proximal end of the stem connected to the distal end of the handle; a heating element with a first surface for contacting infarct scar tissue connected to the distal end of the stem wherein the heating element comprises at least two electrodes and at least one temperature sensor positioned on the first surface for sensing a temperature of infarct scar tissue adjacent to the sensor; an energy source connected to the electrodes via the electric cable; and a regulator connected to the energy source and the temperature sensor of the infarct scar tissue, for controlling the temperature of the infarct scar tissue from about 60 degrees C. to about 99 degrees C. Once the heart has been treated, a restraint is disclosed that allows for the shrinkage to be maintained over time.

This divisional application claims priority based on U.S. patentapplication Ser. No. 10/409,084, entitled “Device For Shaping InfarctedHeart Tissue And Method Of Using The Device” filed Apr. 9, 2003 now U.SPat. No. 7,039.469 which claims priority to granted U.S. Pat. No.6,577,902 entitled “Device For Shaping Infarcted Heart Tissue And MethodOf Using The Device” issued on Jun. 10, 2003.

FIELD OF THE INVENTION

The present invention relates generally to devices and methods that candeliver thermal energy to tissue. More particularly, the presentinvention is directed to devices and methods that can deliver thermalenergy to an area of infarcted heart tissue which shrinks and thickensthe infarcted area to thereby improve cardiac function.

BACKGROUND OF THE INVENTION

The mammalian heart has four chambers for receiving and pumping blood tovarious parts of the body. During normal operation of the heart, oxygenpoor blood returning from the body enters the right atrium via theinferior vena cava, superior vena cava, coronary sinus, or the coronaryveins. The right atrium fills and eventually contracts to expel theblood through the tricuspid valve and into the right ventricle. Theright ventricle fills full of blood and then contracts beginning fromthe apex of the ventricle to the base of the ventricle and forces bloodthrough the pulmonary valve to the pulmonary arteries and to the lungs.The blood becomes oxygenated at the lungs and then returns from thelungs to the left atrium via the pulmonary veins. The left atriumcontracts to expel blood through the mitral valve and into the leftventricle. The left ventricle then fills full of blood and thencontracts beginning from the apex of the ventricle to the base of theventricle and forces blood through the aortic valve, into the aorta, andeventually to the body tissues.

The major blood supply to the heart is derived from the coronaryarteries, two arteries that branch off from the aorta just distal fromthe aortic valve. The right coronary artery provides blood to the rightside of the heart, the left coronary artery supplies blood to the leftside of the heart including the left ventricle. Coronary artery diseaseusually affects the left coronary artery reducing the blood flow to theleft ventricle. When the blood flow supplying oxygen and nutrientscannot meet the demands of the heart, the heart becomes ischemic and thepatient usually suffers from chest pain (angina). When the flow of bloodcompletely stops due to an occlusion of a coronary artery, the heartmuscle becomes very ischemic and will die if blood flow is not restoredin a few minutes.

A myocardial infarction occurs when the heart muscle cells die. The deadmuscle cells are replaced by scar tissue over a period of a few weeks.The scar tissue is not contractile, therefore it does not contribute tothe pumping ability of the heart. In addition, scar tissue is somewhatelastic which further reduces the efficiency of the heart because aportion of the force created by the remaining healthy muscle bulges outof the scarred tissue (i.e., ventricular aneurysm) instead of pumpingthe blood out of the heart.

If the myocardial infarction is fairly large, the scar tissue will formacross the width of the heart and is described as a transmural infarct.The scar tissue will be present both at the endocardial side (inside ofthe heart) and the epicardial side (outside of the heart). Transmuralinfarcts are typically indicated when a patient has a Q-wave infarct asdiagnosed on an electrocardiogram (ECG).

Transmural infarcts can lead to congestive heart failure, a conditionwhere the heart cannot pump enough blood to the body to maintain thesupply of oxygen and nutrients to keep up with the demand. Congestiveheart failure is generally treated with lots of rest, low salt diet, andmedications such as angiotensin converting enzyme (ACE) inhibitors,digitalis, vasodilators, and diuretics. In some myocardial infarcts theinfarct is surgically removed (an infarctectomy or an aneurysmectomy)and the healthy heart is sutured together. This treatment is veryinvasive and has a high morbidity and mortality rate. Ultimately, mostpatients with congestive heart failure die of the condition or are givena heart transplant

The scar that forms in the myocardium is primarily composed of collagen.Collagen demonstrates several unique characteristics not found in othertissues. Intermolecular cross-links provide collagen with uniquephysical properties of high tensile strength and substantial elasticity.The cross-links in collagen are organized such that the threedimensional protein structure of natural collagen forms into a rope likestructure with striations along the rope. When collagen is heated totemperatures above about 60 to 65 degrees centigrade, it is believedthat the cross-links rupture and the protein becomes more globular andless rope like. As the collagen becomes more globular, the collagenshrinks along its axial length. The higher the temperature the collagenis heated, the more globular the collagen becomes and the greater theshrinkage. Collagen can shrink to almost about ½ of its original length.The caliber of the collagen fibers also increases as collagen is heated,up to a four fold increase depending on the temperature.

In a previously filed U.S. patent application Ser. No. 08/768,607 (18Dec. 1996) Michael D. Laufer disclosed the use of heat to treatinfarcted heart tissue, the disclosure of which is hereby incorporatedby reference. The heat would shrink the collagen containing tissue andincrease the pumping efficiency of the heart by decreasing the area thatwas not pumping efficiently. In the Laufer application, it is disclosedthat the scar tissue is to be heated to certain temperature ranges,however, it does not disclose specific means to control the temperatureto the desired range. Additionally, the application did not disclose aspecific device heating element configuration to optimize infarct scarheating throughout the scar.

Animal studies also show that heating the scar tissue to shrink thecollagen gave very good initial clinical results, however, chronicallythe body replaced the denatured collagen with normal collagen and thescar tissue dilated such that the acute results were not maintained.

What is needed therefore is a device and method for heating myocardialscar tissue and controlling the temperature of the tissue to a settemperature range and an optimal heating element to throughly heat theinfarct scar. What is also needed is a device and method that maintainsthe improvement in cardiac function chronically.

SUMMARY OF THE INVENTION

The present invention provides a device and method for treating amyocardial infarction. The present invention is a device forcontrollably heating an infarct scar. One embodiment is a bipolar radiofrequency (RF) device comprising an electric cable with proximal anddistal ends; a handle with proximal and distal ends with the proximalend connected to the distal end of the cable; a stem with proximal anddistal ends with the proximal end of the stem connected to the distalend of the handle; a heating element with a first surface for contactinginfarct scar tissue connected to the distal end of the stem wherein theheating element comprises at least two electrodes and at least onetemperature sensor positioned on the first surface for sensing atemperature of infarct scar tissue adjacent to the sensor; a radiofrequency energy source connected to the electrodes via the electriccable; and a regulator connected to the energy source and thetemperature sensor of the infarct scar tissue, for controlling thetemperature of the infarct scar tissue from about 60 degrees C. to about99 degrees C.

A further embodiment illustrates that the electrodes have a length L, awidth W, and are separated by a space S wherein the space S is less than2 times the length L and no greater than 10 mm, the width W of theelectrodes is greater than 0.2 times the space S and equal or less thanthe length L. This electrode configuration optimizes the treatment area.

Yet another embodiment illustrates a heating element and a temperaturesensor that protrudes from the surface of the heating element. Thetemperature sensor accurately measures the temperature of the adjacenttissue and also serves as an anchor to secure the heating element on abeating heart.

Finally, once the infarct scar tissue has been treated, a reinforcementpatch material is secured over the scar to maintain the new geometry ofthe heart chronically.

The device is used on an infarct scar that has been surgicallyidentified and isolated. The device is placed on the scar and atemperature sensor controlls the amount of energy used to heat the scartissue to a predetermined set point ranging from about 60 degrees C. toabout 99 degrees C. The heat is applied for about 5 to about 60 secondsuntil the area under the device has shrunk. The device is then moved toother areas of the scar until the entire scar tissue has been shrunk.Then a reinforcement patch material is secured over the heat treatedinfarcted scar tissue to prevent dilation during the bodies healingprocess.

The present invention provides advantages of thoroughly heating aninfarct scar, controlling the temperature of the scar, and maintainingthe improved cardiac function over time.

BRIEF DESCRIPTION OF THE DRAWINGS

As used herein, like reference numeral will designate similar elementsin the various embodiments of the present invention wherein:

FIG. 1 is a plan view of a heating device that can deliver radiofrequency energy and monitor temperature;

FIG. 2 is a plan view of a radio frequency generator and controller;

FIG. 3 is an enlarged plan view of the heating device of FIG. 1;

FIG. 4 is an exploded view of the heating device of FIG. 1;

FIG. 5 is a schematic top view of the distal end of the heating device;

FIG. 6 is a bottom view of the heating device;

FIG. 7 is a schematic side cross-sectional view of the heating device;

FIG. 8 is an enlarged view of the temperature monitoring means in circle8 of FIG. 7;

FIG. 9 is a schematic view of an alternate embodiment of the heatingdevice; and

FIG. 10 is a schematic view of the critical dimensions of the electrodeswithin the heating device.

FIG. 11 is a schematic view of the heating zone created by widely spacedelectrodes.

FIG. 12 is a schematic view of the heating zone created by properlyspaced electrodes.

FIG. 13 is a schematic view of the heating zone created by too closelyspaced electrodes.

FIG. 14 is a bottom view of an alternate electrode housing.

FIG. 15 is a cross-sectional view of the electrode housing of FIG. 14taken along line 15-15.

FIG. 16 is a side view of the electrode housing of FIG. 14.

FIG. 17 is a top view of a restraint.

FIG. 18 is a schematic view of an infarcted heart

FIG. 19 is a schematic view of the infarcted heart of FIG. 18 after heattreatment.

FIG. 20 is a schematic view of the infarcted heart of FIG. 18 after heattreatment and placement of the restraint.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention provides a device and method for heatingmyocardial scar tissue to a desired temperature and controlling thedevice to maintain that temperature for a desired period of time.Turning now to FIG. 1, one embodiment of the heating device 10 isgenerally illustrated. The heating device has a proximal end 11 and adistal end 13.

At the proximal end is provided a connector 15 that can be used toconnect to a power supply or an extension cable. A flexible electricalcord 19 is connected to the connector at one end. At the other end ofthe cord is a handle 21 for holding and using the device. Connected tothe proximal end of the handle is a stem 23 which spans from the handleto the heat delivering member 25.

FIG. 2 illustrates a controller box 27 that supplies power to theheating device. The controller box is connected to a standard electricaloutlet and delivers power to the heating device. The controller box isprovided with a display 29 that shows the power settings, duration ofthe power and the temperature the device is to be controlled to. Thetime duration, temperature, and maximum power to be used is controlledby the operator of the device and are adjusted via controllers 28 on thecontrolling box. The box is also provided with a standard on/off switch33 and a connection port 31 for connecting the heating device to thebox.

In the preferred embodiment, the controller box generates standard radiofrequency electrical energy for delivery via the delivering member ofthe heating device. Radio frequency generators are commerciallyavailable from numerous manufacturers, Stellartech Research Corporationin Mountain View, Calif. being one. The controller box can generate fromabout 0.2 watts to 100 watts of power at a frequency ranging from about1 kHz to about 1000 kHz with 460 kHz being presently preferred. The timeduration for the radio frequency generator can be adjusted from about 1sec to about 300 seconds, with a time duration of about 25 to about 60seconds being presently preferred Although the controller box in theillustrated embodiment generates RF energy and controls the RF energy,these functions could be split over different devices such as an RFgenerator being controlled by a separate microprocessor.

The operator of the controller box sets the temperature point, themaximum power to be delivered, and the duration of the power delivery.When the operator of the controller box connects the device and turnsthe power on to the device, the box delivers the maximum power to thedevice until the temperature is reached. The controller then reduces thepower to maintain the temperature and controls the amount of power beingdelivered based on the temperature. The temperature set point can bevaried from about 60 degrees C. to about 100 degrees C., with a rangefrom about 65 degrees C. to about 95 degrees C. being presentlypreferred. As described below, the depth of treatment can be controlledby properly selecting the time and temperature of the treatment withproperly spaced electrodes.

Turning now to FIGS. 3 and 4, the device 10 is further illustrated.Starting at the proximal end 11, the device comprises an electricalconnector 15 such that the device can be connected to a suitable cableor can be connected directly to the controller box. The preferredconnector actually comprises four components: an outer proximal housing43, a multipin solderable connector 45 for attaching the wires from thecable, a fitting 47 for stabilizing the multipin connector, and an outerdistal housing 49 that mates with the outer proximal housing. Otherstandard connectors besides the one illustrated could also be used.

The cable 19 is provided with a plurality of wires. In the presentembodiment four wires, 51, 53, 55, and 57 are used. The wires areinsulated from one another and the insulation on the distal ends arestripped for soldering into the multipin connector. The wires providefor electrical connection from the connector to the heat deliveringmember and temperature sensor. The cable is also provided with an outersheath 18 that is insulated.

The cable spans from the connector to the handle 21. In the preferredembodiment, the handle comprises two halves, a top half 61 and a bottomhalf 63. The axial center of the handle halves has a hollow core 70 toallow for the cable to fit inside the handle. The core's diameter isreduced near the distal end of the handle to form a smaller channel 76.The reduction in the diameter of the hollow core corresponds to thedistal end of the cable sheath. At the proximal end of the hollow core,there are provided indents 72 that when the top half and the bottom halfare fitted together, the indents slightly deform the cable and preventthe cable from rotating or from pulling out of the handle. Also providednear the distal end of the handle in the hollowed out portion is a flatchannel 78 which as described below secures the stem 23 of the deviceinside the handle. The cable is secured by a friction fit within thehandle. It is to be noted that the cable could also be fixed within thehandle by other means well known in the art such as adhesives, welds, orthe like.

The handle is provided with a plurality of holes 73 and threaded holes75 that mate with screws 77. The screws are used to secure the top andbottom halves of the handle together. The handle is also provided withtwo ring members 35 and 39 which fit over the proximal end 67 and thedistal end 71 respectively when the two handle halves are fittedtogether. These rings also secure the two handle halves. Finally, thehandle is provided with ribbing 79 to help the health care practitionerhold the handle while using the device. Although the handle asillustrated comprises two halves that fit together, the handle could beinjection molded using standard molding materials and techniques andformed as one singular unit with the components of the handle sealedwithin the injection molding material.

Turning now to the stem 23, the stem is hollow and fairly sturdy. Thestem can be made from numerous materials such as a metal hypotube andthe like, or it can be made from plastics. A thin hollow heat shrinkingtube 24 is fitted outside the stem and electrically insulates the stemfrom the operator of the device. The insulating tube can be made fromnumerous materials, polyolefin being currently preferred. The stem isflat crimped near the proximal end such that the flat crimp 74 fits intothe flat channel 78 of the handle. The flat channel is not as deep asthe narrow channel and prevents the stem from turning inside the channelor from being pulled out of the channel.

At the distal end of the stem is the heat delivering member which in theillustrated embodiment comprises an electrode housing 26 and a pluralityof electrodes 39. The distal end of the stem fits into a side hole 56 inthe housing. The stem is angled with an angle A that ranges from about120 degrees to about 180 degrees with 160 degrees being presentlypreferred. At the distal end of the stem is a notch 42 that anchors thestem inside the housing when a sealing material 41 is used to seal thehousing and the wires inside the housing as discussed below. Optionally,a display signal 28 such as an LED can be used to give visual feedbackof when the device has RF current going through the device. Such displaysignal would be electronically connected to the controller box and wouldgive a visual display when the controller was delivering energy to theelectrodes.

Turning now to FIGS. 4-8, the housing has a top opening 84 and aplurality of bottom openings 80 that correspond to the electrodes. Alsoprovided in the housing is a side opening 56 for the stem 20 to beinserted. Once the stem is inserted and the electrical connections aremade, the stem is secured with an insulating glue 85 such aspolyurethane and the like.

In the preferred embodiment, there are two electrodes 39 and the size ofthe openings are just larger than the electrodes to make a snug fit.Once the electrodes are placed in the housing, the exposed surface ofthe electrodes project a distance d from the bottom of the housing. Thedistance d can vary from about 0.01 mm to about 1 mm with about 0.1 mmbeing presently preferred. Two wires, 51 and 53, from the cable 19 areelectrically connected to the electrodes via solder connection 78. Thetop opening 84 is large enough to provide room for electricallyconnecting each wire with an electrode. Once the electrodes and wiresare in place the top opening is sealed with sealing material 41 such aspolyurethane and the like. The stem is notch so that the sealingmaterial can wick inside the stem and help bond the stem inside thehousing.

Alternately, the electrodes could be plated onto the housing instead ofbeing fitted into the housing. It is very important that the electrodeshave a smooth surface without any sharp edges or corners. If there aresharp edges or corners, these serve as current risers where the RFcurrent from the RF generator will collect and cause non-uniform heatingwithin the scar tissue. In the presently preferred embodiment theelectrodes have rounded corners and edges and are polished in awater/rock tumbler to insure that the edges are smooth and free of anyburrs or other rough spots. One of ordinary skill in the art could usedifferent techniques to create the electrodes, however the electrodeplacement and location is critical to having a good result as describedbelow.

In the center of the housing is a small hole 81 for a standardtemperature sensing lead. In the preferred embodiment the temperaturesensing lead consists of two different wires 55 and 57 which form atemperature sensor 87 (see FIGS. 6-8). The temperature sensing leadwires are threaded through the side opening 56 and down the centralopening 81 to project from the bottom surface of the housing. In theillustrated embodiment the twisted wires form a thermocouple and have asharp tip 97 for placement into the tissue to be treated. Othertemperature sensors could also be used such as a thermistor or the like.The temperature sensor projects a distance D from the surface to measurethe temperature of the tissue being treated. The distance D can varyfrom about 0.1 mm to about 10 mm with a range from about 1 mm to about 2mm being preferred. The most preferred distance is 1.25 mm. The sharptip and distance D allows the temperature sensor to be placed within theactual scar tissue being heated to measure the tissue that is adjacentto the temperature sensor. Additionally, if the distance D is between 1and 2 mm and the temperature sensor is centered about half-way betweenthe two electrodes as illustrated, then the thermocouple will measurethe tissue at its hottest point. This is due to the fact that the RFenergy being delivered will have the highest current density, and hencetissue temperature, about 1 to 2 mm into the tissue if the electrodespacing is appropriate, see discussion below. Another benefit of havingthe temperature sensor project from the surface of the holder is to havethe sensor serve as an anchor to the device when the device is used on abeating heart. The temperature sensor will pierce the infarcted hearttissue and keep the heating element and the electrode in contact withthe infarcted scar tissue.

When the heating device is used, the temperature of the tissue at thetemperature sensor can be controlled to a specified temperature range byadjusting the power of the RF energy being delivered to the electrodesthrough a temperature control feedback loop. Once the temperature sensoris measuring the desired temperature (85 degrees C. for example) thenthe amount of RF energy being delivered to the electrodes is reduced toa level which maintains the temperature instead of continuing to heatthe tissue to a higher temperature.

Although the preferred embodiment has a single temperature sensor thatprotrudes from the bottom surface of the housing, FIG. 9 illustrates analternate embodiment where there are two different temperature sensors,91 and 93 on the exposed surface of the electrodes. The temperaturesensors are located within the electrodes by drilling a hole in theelectrodes and placing the sensors within the hole. The holes are thenfilled with a potting material such as polyurethane and the like. Leadwires are electrically connected to the sensors for connecting to thegenerator/controller. In the preferred embodiment the sensors arethermocouples that are made out of the lead wires, although othersensors could be used such as thermistors. In this embodiment, thetemperature of the tissue adjacent to the electrodes are monitored andcan be appropriately controlled.

Another aspect of the invention is the size and spacing between theelectrodes. It is desirable to have uniform heating through the infarctscar between the electrodes. To have uniform heating, there needs to bea certain current density through the tissue and through a certain areaof the electrodes. Additionally, the electrodes need to be spaced aparta set length to have the best effect. If the electrodes are too close,the tissue heating occurs primarily on the surface of the tissueadjacent to the electrodes. Tissue located deep under the electrodes donot heat up as well since very little current is traveling through thedeep tissue. If the electrodes are spaced too far apart, then theelectrodes act much more like two separate unipolar electrodes and theheating only occurs right near the edges of the electrodes. The reasonfor this type of heating pattern is that there is too much tissuebetween the electrodes and the current density goes down as the currentfinds many different pathways between the electrodes. Increasing thepower being delivered to the electrodes does not help because thetemperature near the edges of the electrodes will get too hot and willsinge the tissue. Singed tissue is dehydrated and acts like an insulatorand prevents current from traveling through the tissue.

Turning now to FIG. 10, a schematic illustration of the heating element25 is shown where the electrodes 39 have a length L, width W and areseparated by a space between them S. The space S should be no longerthan 2 times the length L. Preferably the space S should be no longerthan the length L and more preferably range from about 0.3 L to about 1L, with 0.625 L being presently preferred. The space S should be nogreater than 10 mm, more preferably less than 6 mm. If the device isused on small mammals, i.e. rats, mice and the like, the space S shouldbe less than 3 mm with the width W of each electrode being 2 mm yieldingat least a 5 mm heat treatment x\zone as described below. If the deviceis used on larger mammals, i.e. humans, sheep, and the like, the space Sshould be no greater then 8 mm. Currently 5 mm space is used for heatingdevices that can treat larger mammals. The width of the electrodes canvary, but should be no smaller than 0.2 times the space S. Currently,the preferred width ranges from about 0.2 S to about 2 S, morepreferably 0.33 S to about 1 S, with 0.8 S being presently preferred.The width W should be equal or less than the length L. Currently thepreferred width ranges from about 0.2 L to about 1 L, more preferably0.33 L to about 0.67 L, with 0.5 L being presently preferred. Thus, thepresently preferred electrode configuration is for the electrodes tohave a length L of 8 mm, a width W of 4 mm, and a spacing S of 5 mm. Theelectrodes also have a thickness which is not illustrated. The thicknessof the electrodes should be as thin as possible but sufficient enough todeliver RF energy without heating because thick electrodes do not heatup and are actually a heat sink taking heat away from the tissue.Currently the thickness of the electrodes is between 0.1 mm and 4 mm,with 1.5 mm thickness being presently preferred.

FIGS. 11-13 schematically illustrate the effect of spacing and the zoneof tissue heating. In FIG. 11, the electrodes 39 are spaced too farapart (greater than 10 mm) and the heating zones 103 created in thetissue 101 are small and widely separated. FIG. 12 illustrateselectrodes that are properly spaced and create one heating zone 105 inthe tissue that penetrates fairly deep into the tissue. In smallmammals, the treatment zone will laterally range from about 5 mm toabout 8 mm, and will penetrate about 1 mm deep, in large mammals, thetreatment zone will laterally range from about 8 mm to about 15 mm, andwill penetrate about 1 to about 3 mm deep. FIG. 13 illustrateselectrodes that are too close to each other. One small heating zone 107is created that does not penetrate deep into the tissue. Presently,using the preferred electrode spacing and dimensions listed above, thetemperature of the tissue being treated can become greater than about 65degrees C. (the shrinking point of collagen) to a depth of about 3 mm ina 5 mm infarct scar using the temperature set point of 95 degrees C. andheating for about 40 seconds. Setting the temperature set point to 90degrees C. and treating for 40 seconds can treat to a depth of about 2mm. Setting the temperature set point to 85 degrees C. and treating for35 seconds can treat to a depth of about 1 mm. Thus, depending on thethickness of the infarct scar, the temperature can be adequatelycontrolled. The heating zone profiles are ideal for treating infarctscar tissue on a beating heart in that the endocardial tissue is kept atbody temperature reducing the risk of thrombosis and embolisms.

Other forms of energy delivery do not as readily provide a controllableheating zone as the present device. For example, laser energy could beused to heat an infarct scar, however the heat would only be generatedat the surface of the heart and would have to conduct through the hearttissue. To generate a deep heating zone, the surface of the heart wouldprobably have to be heated higher than 100 degrees C. which can causeundue desication and damage to the scar tissue. Resistive heating orapplying a hot surface to the scar again would only treat the outermostarea of the scar and would be difficult to treat the tissue deeply.Microwave energy radiates from an antenna and would tend to be moredifficult to control and increase the risk of enocardial thrombosis.

FIGS. 14-16 illustrate a further embodiment of an electrode holder 125.In this embodiment the electrode holder has a plurality of grooves 109on the bottom surface that will come into contact with the tissue to betreated. The grooves, along with the temperature sensor as describedabove, help to stabilize the device on a beating heart by increasing thefriction between the electrode housing and the tissue being treated. Inthis embodiment, the housing is injection molded using electricallyinsulating polycarbonate and then the grooves are machined onto thesurface. Other material besides polycarbonate can be used such aspolysulphone and the like. Additionally, the lateral sides of theelectrode openings 80 have a projection 111 for stabilizing theelectrodes once they are in place. The other reference numbers in FIGS.14-16 correspond to similar components of electrode housing 26 describedabove.

FIG. 17 illustrates a restraint used in the present invention. Therestraint is used to prevent loss of the infarct scar reduction overtime. The restraint in the presently preferred embodiment is a wovenpolyester material that is 10 cm by 10 cm. However, other restraintscould be used such as the patient's pericardium or other autologousconnective tissue such as fascia lata, bioabsorbable materials,biodegradable materials, polytetraflouroethylene (PTFE), polypropylene,polyethylene, polyurethane, and other materials well known in thesynthetic medical fabric device industry.

FIG. 18 schematically illustrates a heart 141 with an infarcted zone143. After the treatment, the treated infarcted zone 145 (see FIG. 19)is dramatically reduced in area. Finally, the restraint is secured ontothe heart with tack sutures 151 and running sutures 153. Alternatively,the restraint could be adhered to the heart using tissue adhesives suchas cyanoacrylate, fibrinogen glue, and the like.

The heating device is used in the following manner. First a mammal witha myocardial infarction is evaluated to ensure that the infarct area isstable and has minimal inflamation. This occurs after at least 4 weekspast the onset of the infarction and may last as long as about 12 weeksdepending on the mammal to be treated. In humans, at least 6 to 8 weekspost acute myocardial infarction is needed to reduce the inflamation.The evaluation can include ECG, stress ECG, cardiac imaging(angiography, ventriculography, echocardiography, fluoroscopy, MRI,nuclear medicine scans, and the like) functional testing and otherstandard medical cardiovascular evaluations. Once a proper patient isidentified, the patient is prepared for surgery.

In the operating room, the patient's chest is incised and the heart isexposed. It is contemplated that the chest incision can range from asmall minimally invasive incision to a full sternotomy. Once the heartis exposed the area of infarction is identified. The infarcted area doesnot contract like the normal heart muscle. It may contract less(hypokinetic) not contract at all (akinetic) or even bulge out when therest of the heart contracts (dyskinetic). Additionally, the infarct is adifferent color and texture than the rest of the heart. The infarct,being mainly made up of collagen, is whiter and stiffer than the normalmuscle of the heart which is red and contractile. If the infarct iscovered by adipose tissue, the adipose tissue is removed by standardsurgical means.

It is contemplated that the present invention would be used on the heartwhile the heart is beating. This way the patient has less chance ofhaving complications from the operation since the patient will not be onheart-lung bypass. However, if the situation dictates, the presentinvention can be used on a patient that is on heart-lung bypass bycarefully regulating the set point for the temperature sensor and theamount of time for the treatment.

After the heart is exposed, the heating device is placed on theinfarcted area RF energy is then delivered to the device via the radiofrequency generator/controller. The RF energy is delivered to heat theinfarcted tissue to a temperature greater than 60 degrees C., preferablygreater than 65 degrees C., but less than 100 degrees C. If the tissueis heated to greater than 100 degrees C. for any length of time, thetissue may dessicate and char, which then insulates the surroundingtissue from the RF current and prevents good heating. In the presentembodiment, if the temperature sensor measures a temperature of 102degrees C. or greater for two seconds it will automatically shut off.Preferably RF energy is delivered from about 0.2 watts to 100 watts ofpower, at a frequency ranging from about 1 kHz to about 1000 kHz, forabout 1 second to about 300 seconds. In the current preferred method, upto 20 watts of power can be delivered to have the tissue reach atemperature near the temperature sensors between about 65 and 95 degreesC., with set points of 85, 90 and 95 degrees C. being presentlypreferred. The frequency used is about 460 Khz and usually 30 to 40seconds per treatment is used to ensure a good depth of the heat zonecreated.

When the collagen reaches a temperature above its glass transitionpoint, the collagen denatures and changes shape from a long linearprotein to a globular protein. This change in shape causes the collagenin the infarct to shrink. Once some of the collagen has shrunk, morecollagen is now being exposed to the RF energy and being heated and morecollagen will shrink. Eventually a steady state is reached where nofurther collagen will shrink based on the location of the heatingelement. This usually occurs within 20 to 40 seconds. Once this occurs,the heating element is moved to another area of the infarct that has notbeen treated and RF energy is applied to this area. In the preferredmethod, the infarct scar is treated in the center of the scar first.After the first treatment, the heating device is moved in a tilingdirection from the center, overlaying only a small area that has beentreated and working to the edges of the scar. Once the entire infarctedarea is treated any areas that appear to need further treatment areretreated to ensure that the entire infarcted area was treated. Care istaken to not treat healthy contracting myocardium in that the treatmentcould injure healthy myocytes.

Once the device has been properly used, the treated and altered infarctis about one half the size of the original infarct. This reduction inthe surface area of the infarct reduces the diastolic and systolicvolumes in the heart. Additionally, the heart no longer has a large areaof non-contracting muscle, and the rest of the heart can now pump betterand more efficiently. The net result is that the cardiac function of theheart is improved, and this improvement can be measured by a reductionin volume and an increase in ejection fraction (the fraction of bloodthat is pumped out of the heart during each stroke).

A restraint is then placed over the treated scar tissue. The restraintis trimmed to the appropriate size and shape of the infarct scar. Therestraint is then sutured over the infarct zone to prevent expansion ofthe treated site. The restraint is tacked with at least three sutures151 (see FIG. 20). The sutures are placed just within infarct zone toavoid injuring uninvolved myocardium and at least 3 mm into the materialto prevent sutures tearing loose. The restraint is drawn as taut aspractical and the perimeter of restraint is secured with a runningsuture line 153 between the tack sutures. The sutures are placed nogreater than 3 mm apart. The suturing is preferably performed at thebeginning of diastole (minimal pressure and volume) to ensure thetightest fit of the restraint. The surgery is then completed in thecustomary manner.

EXAMPLE 1

Adult female Sprague-Dawley rats are anesthetized, intubated,ventilated, and the chest incised. The left main coronary artery isvisualized and ligated. The chest and skin is closed. This procedurecreated a large myocardial infarction over the left ventricle of theheart.

After 6 weeks, the rats received echocardiography to determine theextent of the infarcted area, to measure the diastolic area, measure thesystolic area, and to measure the fractional shortening of the heart(Fractional shortening is similar to ejection fraction, however ejectionfraction measure the volume of blood ejected during each stroke and thefractional shortening measures the change in linear distance between thewalls of the left ventricle. Fractional shortening is used in manyanimal experiments to assess cardiac function.)

The rats are then anesthetized, intubated, and ventilated and the chestopened. The infarct scar is visualized and sutures are placed around theinfarct scar. The distances between the sutures are measured. A heatingdevice is placed on the infarct scar. The heating device has twoelectrodes where each electrode has a length of 2 mm, a width of 1 mmand the space between the electrode is about 1.5 mm. Each electrode hasa temperature sensor in the center of the electrode and the controllercontrols the RF power such that neither temperature sensor will sense atemperature greater than 85 degrees. A maximum of 5 watts are deliveredto the electrodes.

Once the heating device was in place in the center of the infarct scar,RF energy is delivered to the electrodes for 30 seconds. After about 15seconds of RF delivery, the infarct scar starts to shrink, and afterabout 20 seconds a steady states is reached. If the scar was largeenough, the treatments are repeated on areas of the scar adjacent to thetreated areas. After the treatment the scar would be about half itsoriginal size. The distance between the sutures are measured again andthe incisions are closed.

After the surgery echocardiography is repeated to measure the diastolicarea, the systolic area, and the fractional shortening. The resultsshowed that the distance between the sutures reduced up to a maximum of50%. The diastolic and systolic areas were significantly reduced. Thefractional shortening improved up to about 50%. Long term follow upechocardiography is repeated which demonstrated dilation of thetreatment area with little difference from control animals.

EXAMPLE 2

Adult female Sheep are anesthetized, intubated, ventilated, and thechest incised. The left descending coronary artery is visualized andligated about ⅓ up from the apex to the base of the heart. Diagonalbranches are also ligated about ⅓ up from the apex to the base of theheart. The chest and skin is closed. This procedure created a largemyocardial infarction over the left ventricle at the apex of the heart.

After about 12 weeks, the sheep received echocardiography to determinethe extent of the infarcted area, to measure the diastolic volume,measure the systolic volume, and to measure the ejection fraction heart.

The sheep are then anesthetized, intubated, and ventilated and the chestopened. The infarct scar is visualized and piezo-electric crystals areplaced around the infarct scar. The crystals are from SonometricsCorporation London Canada and a Digital Sonomicrometer from the samecompany is used to analyze the distances between the crystals. A heatingdevice is then placed on the infarct scar. The heating device has twoelectrodes where each electrode has a length of 8 mm, a width of 4 mmand the space between the electrode is about 5 mm. The heating elementhas a temperature sensor located between the electrodes that protrudes 1mm from the bottom surface of the heating element. The temperaturesensor has a sharp point which is inserted into the infarct scar tissueand helps to keep the heating element stable and on the same location ofthe heart. The temperature sensor is used by the controller to controlthe RF power such that the temperature sensor will sense a temperatureof the tissue no greater than 95 degrees. A maximum of 20 watts aredelivered to the electrodes.

Once the heating device was in place in the center of the infarct scar,RF energy is delivered to the electrodes for 30 seconds. After about 15seconds of RF delivery, the infarct scar starts to shrink, and afterabout 20 seconds a steady states is reached. The treatments are repeatedon areas of the scar adjacent to the treated areas in a spirally outwardtiling pattern to treat the entire scar. Up to 30 treatments are used totreat the entire scar. After the treatments the scar would be about halfits original size.

A restraint is then placed over the treatment area to keep the heartsfrom dilating. The restraint is secured using three tack sutures intothe edge of the infarcted area and a running suture between the tacksutures.

After the surgery the distance between the crystals is analyzed andechocardiography is repeated to measure the diastolic volume, thesystolic volume, and the ejection fraction. The results showed that thedistance between the crystals reduced, the diastolic volume reduce, thesystolic volume reduced and the ejection fraction increased up to about50%. At ten weeks post surgery the measurements are repeated anddemonstrate continued benefit from the heat treatment.

While several particular embodiments of the invention have beenillustrated and described, it will be apparent that variousmodifications can be made without departing from the spirit and scope ofthe invention. Accordingly, it is not intended that the invention belimited except as by the issued claims that ultimately come from thisapplication.

1. A heating element for heating an infarct scar within heart tissuecomprising: a plurality of electrodes for creating a heat zone withinheart tissue, the infarct scar including collagen, wherein thetemperature of the heart tissue heated by said electrodes is from about60 degrees C. to about 99 degrees C. and wherein said heat zonepenetrates at least 1 mm into said scar and laterally extends a distanceof at least 5 mm across said scar to optimally reduce the size of saidscar, the electrodes having a length L, a width W and being separated bya space S wherein the space S is greater than 0.3 times the length L andless than the length L, the width W of the electrodes is greater than0.2 times the space S and equal or less than the length L.
 2. Theheating element of claim 1 wherein the heat zone laterally extends atleast 8 mm across said scar.
 3. The heating element of claim 1 whereinthe heat zone is substantially uniform between the electrodes.
 4. Theheating element of claim 1 wherein the electrodes are positioned in ahousing having a flat surface and wherein the space S is the spaceseparating the electrodes on the flat surface.
 5. The heating element ofclaim 4, wherein a surface of the electrodes project a distance d fromthe flat surface, and wherein the distance d is between 0.01 mm and 1mm.
 6. The heating element of claim 1 wherein the plurality ofelectrodes are plated onto a housing having a flat surface and whereinthe space S is the space separating the electrodes on the flat surface.7. A heating element for heating an infarct scar comprising: a pluralityof electrodes for creating a heat zone within the infarct scar whereinthe temperature of heart tissue heated by the electrodes is from about60 degrees C. to about 99 degrees C. and wherein said heat zonepenetrates at least 1 mm into said scar and laterally extends a distanceof at least 5 mm across said scar, the electrodes having a length L, awidth W and being separated by a space S wherein the space S is greaterthan 0.3 times the length L and less than the length L, the width W ofthe electrodes is greater than 0.2 times the space S and equal or lessthan the length L.
 8. The heating element of claim 7 wherein the heatzone laterally extends at least 8 mm across said scar.
 9. The heatingelement of claim 7 wherein the heat zone is substantially uniformbetween the electrodes.
 10. The heating element of claim 7 wherein theelectrodes are positioned in a housing having a flat surface and whereinthe space S is the space separating the electrodes on the flat surface.11. The heating element of claim 10, wherein a surface of the electrodesproject a distance d from the flat surface, and wherein the distance dis between 0.01 mm and 1 mm.
 12. The heating element of claim 7 whereinthe plurality of electrodes are plated onto a housing having a flatsurface and wherein the space S is the space separating the electrodeson the flat surface.